Heretofore, with respect to a hexahydropyridazine-1,2-dicarboxy derivative: ##STR2## a process has been proposed, for example, as disclosed in Arch. pharm. 295,526-32(1960), wherein diethylhydrazine dicarboxylate and dibromobutane are reacted in the presence of metal potassium using dimethylformamide as a solvent to obtain diethylhexahydropyridazine-1,2-dicarboxylate.
However, the above conventional process has a problem that metal potassium which is difficult to handle, is required to be used, and besides, the yield in the cyclization is as low as 16%.
The present invention has been accomplished for the purpose of solving the above-mentioned problem of the prior art and providing a process which is an industrial process and which is capable of producing a hexahydropyridazine-1,2-dicarboxy derivative in good yield.